Author Topic: Advantages of 25mm tyres over 28mm  (Read 40537 times)

Jonah

  • Audax Club Hackney
Advantages of 25mm tyres over 28mm
« on: January 23, 2012, 07:52:13 am »
I have recently changed tyres from Gator Skin 28mm's to 25 mm's - I have used the 28mm's for long rides and would expect that the 25mm would be less comfortable - so far so good but my trial has just started.  I am more interested in finding out the difference when climbing.  I rode the Hills & Mills AAA 1.75 on Saturday and I am not sure that the 25mm helped?  I found it harder than a similar GdS AAA ride completed  last year.  Is this just my imagination and does it make any real difference (I would expect less resistance on a narrower tyre) or am I just fat from Christmas?

LittleWheelsandBig

  • Whimsy Rider
Re: Advantages of 25mm tyres over 28mm
« Reply #1 on: January 23, 2012, 08:11:14 am »
For the same tyre construction, rolling resistance increases as width drops. Weight and wind resistance drops though.
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vorsprung

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Re: Advantages of 25mm tyres over 28mm
« Reply #2 on: January 23, 2012, 09:33:28 am »
Another advantage of 25mm over 28mm is that there is more choice of better compounds and faster tyres in 25mm

Without getting into the whole Gatorskin love it or hate it debate I suggest if you want a faster tyre you use a 25mm Michelin Pro Race.  They are also more comfortable than 25mm Gatorskins as the casing is more flexible.  They are noticeably faster and very much more grippy.

As for durability, the old 25mm Pro Race 2's I've used have been plenty good enough, doing various rides without any punctures or any other problems.

Like I say this isn't a Gatorskin hate comment.  My point is that if you go from 28mm to 25mm there is more choice of more interesting fast tyres.
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Wothill

  • over the hills and far away
Re: Advantages of 25mm tyres over 28mm
« Reply #3 on: January 23, 2012, 09:55:57 am »
I think that's right about different types of tyre making a big difference. I think the most comfortable tyres I used were 23mm Corsa CX. They cost a bit much now though.

Another point that is sometimes overlooked is that fatter tyres (of the same type) may be more comfortable but only if you reduce the pressure. It's mainly the ability to ride at a lower pressure that makes a fat tyre soak up road roughness better than a narrow tyre of the same construction. Of course, if you reduce the pressure you increase the rolling resistance.

Alf

border-rider

Re: Advantages of 25mm tyres over 28mm
« Reply #4 on: January 23, 2012, 10:00:07 am »
Of course, if you reduce the pressure you increase the rolling resistance.

On rough surfaces (including chip&tar) the extra cushioning decreases vertical movement of the bike & rider which can itself be a substantial loss mechanism. You find sometimes that if you let a couple of psi out you actually go faster on some roads

Re: Advantages of 25mm tyres over 28mm
« Reply #5 on: January 23, 2012, 10:19:56 am »
Andy Wilkinson uses a suspension seatpost on his bike, I was going to say TT bike, but he only has the one. So his unsprung weight is lower. It would be interesting to measure the effect on sidewall deformation. It may be that using a suspension seatpost has the same benefits as high tpi tyres at less cost.

Wothill

  • over the hills and far away
Re: Advantages of 25mm tyres over 28mm
« Reply #6 on: January 23, 2012, 10:21:22 am »
That's true about road roughness; there is always a caveat. It would be interesting to know how rough the road had to be before that happened. It would also be interesting to know the pressures at which tyres of different widths had the same rolling resistance, eg 28mm at 90psi = 25mm at 100psi = 23 at 110, etc

Re: Advantages of 25mm tyres over 28mm
« Reply #7 on: January 23, 2012, 10:23:57 am »
Another advantage of 25mm over 28mm is that there is more choice of better compounds and faster tyres in 25mm
And more sophisticated tyres, with better construction.

I would have doubted what vorspung has said if I hadn't switched from 28mm continental tyres to 25mm Krylion Carbon. These have a very flexible carcass and Michelin recommend lower pressure than most use. The recommended pressures work, tho'.
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AndyH

Re: Advantages of 25mm tyres over 28mm
« Reply #8 on: January 23, 2012, 10:51:38 am »
I suggest if you want a faster tyre you use a 25mm Michelin Pro Race.
+1, best tyres I've used at a sensible price. Durable as well, I'm still using a Pro Race 3 (23mm) on the front of one set of wheels that I put on in July and has done about 4000Km. Not bad for a 200 ish gram tyre. The rear managed about 3000.

As for speed, there are so many variables noted upthread that it's hard to be definitive, but generally the harder / narrower / lighter the tyre the faster it will go. 25 is the widest I go, I'd struggle with mudguard clearance otherwise. I very rarely alter the pressure in mine, just pump them up to whatever the manufacturer says.

Biggsy

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Re: Advantages of 25mm tyres over 28mm
« Reply #9 on: January 23, 2012, 11:08:30 am »
For the same tyre construction, rolling resistance increases as width drops.

I'm not convinced that's true if air pressure is increased as width is reduced.  Up to a point, anyway.  The "point" might be 25mm.
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Biggsy

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Re: Advantages of 25mm tyres over 28mm
« Reply #10 on: January 23, 2012, 11:18:05 am »
I have recently changed tyres from Gator Skin 28mm's to 25 mm's - I have used the 28mm's for long rides and would expect that the 25mm would be less comfortable - so far so good but my trial has just started.  I am more interested in finding out the difference when climbing.  I rode the Hills & Mills AAA 1.75 on Saturday and I am not sure that the 25mm helped?  I found it harder than a similar GdS AAA ride completed  last year.  Is this just my imagination and does it make any real difference (I would expect less resistance on a narrower tyre) or am I just fat from Christmas?

I reckon a properly inflated 25mm tyre has lower rolling resistance than a properly inflated 28mm tyre of the same model on a good smooth surface.  The 25mm though may not roll as well on bumpy surfaces or if under-inflated (for the load weight and the surface).

See another recent-ish thread on The Knowledge discussing tyre weight and climbing.

Often your tyre size is restricted by what the bike can take, anyway.
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mattc

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Re: Advantages of 25mm tyres over 28mm
« Reply #11 on: January 23, 2012, 11:28:38 am »
http://yacf.co.uk/forum/index.php?topic=30527.0 Testing Rolling Resistance

4 pages. We never agreed much - and doubt we ever will!

(Although I think most agreed that roughness-of-surface is a big factor, just as Biggsy says.)
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Jonah

  • Audax Club Hackney
Re: Advantages of 25mm tyres over 28mm
« Reply #12 on: January 23, 2012, 02:09:01 pm »
Thanks for the wealth of information  :thumbsup:- I googled the subject prior to posting and found hardly anything. 

"Just one more thing..."  If I'm climbing a very steep hill (you know, the type of hill where your front wheel lifts and the tendons behind your knees feel like they are going to snap) with an uneven surface would I be at an advantage using 28mm (or wider) tyres due to the extra grip that they may afford over a 25mm with the same pressure?

Re: Advantages of 25mm tyres over 28mm
« Reply #13 on: January 23, 2012, 02:11:52 pm »
Thanks for the wealth of information  :thumbsup:- I googled the subject prior to posting and found hardly anything. 

"Just one more thing..."  If I'm climbing a very steep hill (you know, the type of hill where your front wheel lifts and the tendons behind your knees feel like they are going to snap) with an uneven surface would I be at an advantage using 28mm (or wider) tyres due to the extra grip that they may afford over a 25mm with the same pressure?

Jonah, I think I know the kind of hill you have in mind.  You're determined not to change that cog, aren't you!  Have you got your new bike yet?

LittleWheelsandBig

  • Whimsy Rider
Re: Advantages of 25mm tyres over 28mm
« Reply #14 on: January 23, 2012, 02:12:16 pm »
There is no extra grip either way. A bigger tyre gives a bigger gear though.
Wheel meet again, don't know where, don't know when...

Re: Advantages of 25mm tyres over 28mm
« Reply #15 on: January 23, 2012, 04:25:34 pm »
"Just one more thing..."  If I'm climbing a very steep hill (you know, the type of hill where your front wheel lifts and the tendons behind your knees feel like they are going to snap) with an uneven surface would I be at an advantage using 28mm (or wider) tyres due to the extra grip that they may afford over a 25mm with the same pressure?

At the sort of speed you are likely to climbing a hill like that, rolling resistance probably doesnt come into it.   Weight of tyre (or in my case weight of "spare tyre") is going to count for a lot more.    Coming down the other side can be a bit "interesting" on narrow tyres pumped up hard, especially if at all wet.   I can tell you that Hardknott in the rain on 25 mm is pretty buttock-clenching, stopping to lower tyre pressures was just not an option.   

Re: Advantages of 25mm tyres over 28mm
« Reply #16 on: January 23, 2012, 04:30:40 pm »
I think the only time tyre width is a factor in this is when the surface has lots of debris, washed on stones, that kind of thing. In those circumstances, balloon tyres will be better as they have less of a tendency to skip off small stones.

But 25vs28 makes no difference to grip.
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Biggsy

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Re: Advantages of 25mm tyres over 28mm
« Reply #17 on: January 23, 2012, 04:36:55 pm »
Regarding weight: the Gatorskin is so light that the difference between the 28 and 25mm versions will only be an insignificant number of grams.
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Hummers

  • It is all about the taste.
Re: Advantages of 25mm tyres over 28mm
« Reply #18 on: January 23, 2012, 06:54:03 pm »
I noticed a marked difference in ride comfort between Conti 4 Season 25 and 23mm tyres and no really appreciable reduction of speed.

H


Re: Advantages of 25mm tyres over 28mm
« Reply #19 on: January 23, 2012, 07:11:17 pm »
...... It would also be interesting to know the pressures at which tyres of different widths had the same rolling resistance, eg 28mm at 90psi = 25mm at 100psi = 23 at 110, etc
It's not as simple as that.  My 15st on a 25mm tyre requires significantly more pressure to retain the same profile as someone rather lighter like (for instance) MattC.  I have never detected any difference between 25 and 28 in terms of comfort or rolling resistance (using Gatorskins or Panaracer Pasala TG)

PaulF

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Re: Advantages of 25mm tyres over 28mm
« Reply #20 on: January 23, 2012, 07:15:17 pm »
I think the only time tyre width is a factor in this is when the surface has lots of debris, washed on stones, that kind of thing. In those circumstances, balloon tyres will be better as they have less of a tendency to skip off small stones.

But 25vs28 makes no difference to grip.

But as you can run the 28s at a lower pressure they'll have a larger contact patch and therefore more grip?

Jonah

  • Audax Club Hackney
Re: Advantages of 25mm tyres over 28mm
« Reply #21 on: January 23, 2012, 07:19:34 pm »
Thanks again folks - looks like it's the Christmas fat afterall.

Jonah, I think I know the kind of hill you have in mind.  You're determined not to change that cog, aren't you!  Have you got your new bike yet?
[/quote]

Were you thinking of Buttertubs Pass, Tan Hill, or the Trough of Bowland?  Just waiting for the cranks to arrive for the new bike - she will hopefully be ready in time for my next dose of Northern Punishment: the Dales Delight - are you in?

KieronY

  • N007
Re: Advantages of 25mm tyres over 28mm
« Reply #22 on: January 23, 2012, 07:53:43 pm »
You could try the rather boutique Grand Bois Cerf.

They are something like a souped-up Panaracer Pasala and at 26mm offer a bit of compromise between 25mm and 28mm.

The ride quality is as good as they say. I changed to these after PBP and they feel much livelier and more comfortable than my old leaden and dead feeling, though very durable, Gatorskins.

Previously, at the original price, I would have said they are too expensive but new lower pricing seems about right.


Re: Advantages of 25mm tyres over 28mm
« Reply #23 on: January 23, 2012, 09:00:14 pm »
They look very 'old school'. Would be fantastic to stick on an old classic bike.

Let us know how well they wear.
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Feanor

  • It's mostly downhill from here.
Re: Advantages of 25mm tyres over 28mm
« Reply #24 on: January 23, 2012, 10:27:38 pm »
I suggest if you want a faster tyre you use a 25mm Michelin Pro Race.
+1, best tyres I've used at a sensible price. Durable as well, I'm still using a Pro Race 3 (23mm) on the front of one set of wheels that I put on in July and has done about 4000Km. Not bad for a 200 ish gram tyre. The rear managed about 3000.

I'm going to disagree about the durability of the Pro Race 3.

It's my summer tyre of choice, and they 'feel' fast and responsive and all, but durability has been poor here.   They seem to suck in every little bit of sharp road grit, which leaves little cuts on them but more importantly, the litle bit of sharp grit which worms its way through to the inside.  A visual inspection of the tyre will be OK, showing some minor cuts in the rubber, and a grope around the inside is OK.   But there's nasty pointy sharp thing embedded inside the rubber.

Come autmn, these *need* to come off, otherwise I have multiple faerie visits on a 200k ride.

This may be specific to my roads, which are a bit rough and pot-holley with lots of loose sharp grit and stuff esp. around winter.

But really, except perhaps on smooth tarmac, I can't rate their durability.